1. Field of the Invention
The present invention relates to presence systems which enables a user on a network to refer to presence information of other users.
In the present invention, a presence system includes a server and clients. The server stores presence information of a user agent who operates a client and distribute the presence information to other clients. The owner of the distributed presence information is referred to as a “presentity”. The operator of a client that receives the presence information of the presentity is referred to as a “watcher”. Presence information means any information related to the presentity, and may include text messages and icon files that indicate status, personal information that indicates residential addresses or communication addresses, and the like. Another user agent whose presence information that a user agent wishes to subscribe to is referred to as a “buddy” of a user agent. A list of the buddies of a user agent is referred to as a “buddy list”.
2. Description of Related Art
In recent years, there has been a rapid spread of communication services that enable users to connect with the Internet all the time from homes and workplaces, and mobile telephones that are connectable to the Internet have also been widely used. As such communication infrastructure has been built up, presence systems, by which a user can reference the presence information of other users on a network, have been more commonly available in people's daily lives and in workplaces. Instant messaging systems (hereafter referred to as “IM systems”) have also been widely used, in which users exchange text messages one another in real-time. Among presence systems, there exits a system that handles text messages as part of the presence information; for this reason, the presence system herein is meant to include such IM systems.
In a presence system, a presentity owns presence information. Each presentity can freely set his/her own presence information. A user registers a presentity whom the user has interest in, i.e., a buddy, to a server. The requesting user becomes a watcher of the buddy, and acquires presence information of the buddy.
Recently, it is not uncommon that one user uses a plurality of terminals. In presence systems as well, there exists a system designed for a use such that one user uses a plurality of terminals. For example, Microsoft Messenger (a registered trademark) enables one user to use both a terminal at work and a terminal at home by switching between them. When a user updates a buddy list with a terminal at the workplace, the latest buddy list is uploaded to the server. Thereafter, when a terminal at home is connected to the server, the buddy list in the terminal at home is compared with the buddy list in the server and the latest buddy list is downloaded from the server. Thus, Microsoft Messenger performs synchronization of buddy lists between a plurality of terminals used by one user.
However, in the foregoing presence system, it is not assumed that one user simultaneously uses a plurality of terminals. For this reason, if one user wants to simultaneously connect a plurality of terminals with the server, only one of the terminals can connect with the server at a time, which is inconvenient. Moreover, even if the foregoing presence system allows one user to connect a plurality of terminals, it is only when each of the terminals connects with the server that the buddy list in each terminal obtains the latest status. Thus, a system has not yet been conceived that after a plurality of terminals have connected with a server, a change in the buddy list of a terminal is reflected in the buddy list of another terminal. In other words, it has not yet been possible to provide a system such that a dynamically changing buddy list is synchronized between a plurality of terminals used by one user.
Furthermore, in the foregoing presence system, display formats of the buddy lists displayed on the terminals may differ from one terminal to anther. The display format of a buddy list can be set according to user's preferences by setting display attribute information such as display names and categories of the buddies. However, the display attribute information is only valid in each one of the terminals. Accordingly, if the user wants to display the buddy list in a plurality of terminals in the same format, he/she has to set the display attributes in each of the terminals, which is a cumbersome operation.
In addition, in a presence system, a user may be notified of the presence information of a presentity who is not specified by the user as his/her buddy. This is undesirable for security reasons. Moreover, the user may find offensive if he/she is notified of the presence information of unknown presentity unilaterally.
It is an object of the present invention to allow a presence system in which one user uses a plurality of terminals to synchronize dynamically changing buddy lists between the terminals.
It is another object of the present invention to allow a presence system in which one user uses a plurality of terminals to synchronize display formats of the buddy lists in the terminals without increasing a burden on the user.
It is further another object of the present invention to tighten the security of a presence system and to prevent a presence notification that is a nuisance for the user.